1. Field of the Invention
The present invention generally relates to copier machines, printers, facsimile devices, or the like which have a plurality of image-formation units vertically positioned, and particularly relates to prevention of dirt made by a development agent inside the device or in a periphery thereof.
2. Description of the Related Art
For the purpose of enhancing image-formation speed, an image-formation device creating full-color images, such as a full-color copier machine, are provided with a plurality of image-formation units, and an example of such a configuration can be found, for example, in Japanese Laid-open Patent Application No.4-221663 and Japanese Laid-open Patent Application No.4-246573.
An image-formation device disclosed in these documents includes a base-body unit having a control device and a detachable sheet-supply tray, and further includes a plurality of image-formation units stacked one over another on the base-body unit. Each of the image-formation units has a case, and contains within the case an image-formation element equipped with alignment/mount parts provided at an upper end and a lower end thereof. The image-formation element is movable inside the case. Each of the image-formation units transfers a toner image from a photosensitive body thereof onto a sheet, and each toner image corresponds to a respective color, i.e., cyan, magenta, yellow, or black, thereby creating a full color image on the sheet.
Each of the image-formation units has the image-formation element thereof movably contained in the case, and the image-formation element includes the photosensitive body, an image-development unit, etc. The image-formation elements of the plurality of image formation units are stacked one over another where a connection between two elements situated one over the other is provided by the alignment/mount parts. This configuration allows a free choice to be made with regard to the number of image-formation elements, and has an advantage in that an increase in the number of image-formation elements does not result in an increase in an area occupied by the device.
Since a respective toner image of each image-formation unit needs to be transferred from a respective photosensitive body to a sheet, the case of the image-formation unit inevitably has an opening at a position of the photosensitive body for the purpose of transferring the image. This opening of the case allows toner, serving as a development agent, to spread from inside of the case to outside of the case, resulting in toner being accumulated inside the device as dirt. Further, replacement of an image-formation unit or refilling of toner is likely to result in spreading of toner, creating dirt in a periphery of the device. Because of these problems, excessive maintenance is required.
In consideration of these shortcomings, accordingly, there is a need for an image-formation device which can avoid making dirt inside the device and in a periphery thereof, thereby insuring formation of a high-quality image.